1. Anatomy of the Abdomen in Computed Tomography
Michael C. Ficorelli, RT

2. Lesson Description
To explain the various exams pertaining to the abominal cavity using computed tomography, incorporating cross sectional anatomy from images

3. Lesson Description
To be able to identify anatomy of the abdominal cavity. Understand the clinical indications for exams of the abdomen. To understand the methods of patient scanning, positioning, and protocols. To understand indications for contrast.

4. CT of the Abdomen

5. Abdominal Cavity
Region between the diaphragm and the sacral promontory (L-5 / S-1)
Divided into 4 quadrants or 9 regions
Contains:
Liver
Gallbladder
Biliary System
Pancreas
Spleen
Adrenal Glands
Kidneys
Ureters
Stomach
Intestines
Vascular Structures

6. Abdominal Cavity

7. Peritoneum
Thin serous membrane which lines the walls of the abdominal cavity
2 Layers separated by fluid used for lubrication
Parietal Peritoneum – lines abdominal wall
Visceral Peritoneum – lines organs
In males, cavity is closed. In females, cavity extends outward via uterine tubes, uterus and vagina
Folds extend between organs allowing them to hold position and enclose the vessels and nerves between them
Mesentery – encloses intestines
Omentum – Attached to stomach
Greater omentum – greater curvature to spleen
Lesser omentum – lesser curvature to duodenum

8. Peritoneum
Contains:
Stomach, 1st part of duodenum, jejunum, ileum, cecum, appendix, transverse colon, sigmoid, upper 1/3 or rectum, liver, spleen and pancreas
In women – fallopian tubes and ovaries

9. Peritoneum
Peritoneal ligaments connect organs to one another or to the abdominal wall
Numerous but most important
Falciform ligament – liver to anterior abdominal wall and diaphragm which divides the liver into 2 lobes

10. Retroperitoneum
Structures posterior to peritoneum yet lined by it anteriorly
Kidneys, Ureters, Adrenal Glands, Pancreas, Duodenum, Ascending and Descending colon, Aorta, IVC, Bladder, Prostate, and Uterus

11. Liver
Largest organ in abdomen which is divided into 4 lobes (or 8 segments based on its vascular system) taking up the right upper quadrant
Left and right are largest
Caudate – inferior and posterior
Quadrate – inferior and anterior
Bordered superiorly, anteriorly and laterally by the diaphragm, medially by the stomach and duodenum which has many functions
Metabolic regulation
Hematologic regulation
Bile production
Has dual blood supply – arterial and venous

12. Portal Hepatic System
Route liver receives venous blood from gastrointestinal tract
Portal Vein – in retroperitoneum by union of SMV and splenic vein
Branches out into right and left portal veins
Right hepatic vein enters the IVC laterally
Middle hepatic vein enters IVC anteriorly
Left hepatic vein enters IVC on left anterior surface

13. Hepatic Arterial
Common Hepatic artery arises from one of the 3 celiac arteries and divides down to proper hepatic the right and left hepatic…

14. Biliary System Gallbladder and bile ducts
Gallbladder is organ which stores and concentrates bile prior to sending to duodenum
Bile ducts run beside hepatic arteries and veins
Common Bile Duct – originates at junction of common hepatic duct (united right and left hepatic duct) and the cystic duct (duct of gallbladder)
CBD empties into the duodenum along with pancreatic duct at the Ampulla of Vater through the Sphincter of Oddi

15. Pancreas Located in retroperitoneum
Long, narrow organ lying posterior to the stomach and extends transversely at an oblique angle between the duodenum and splenic hilum
Head – broad and flat; lies nestled in the curve of the duodenum around L – 2 / L – 3
Body – largest anterior portion
Tail – extends to the left anterior pararenal space
Functions in endochrine system by producing insulin and glucagon
Also produces digestive enzymes
Main pancreatic duct carries products into the duodenum through the ampulla of vater

16. Pancreas

17. Spleen and Adrenal Glands
Spleen – in peritoneum, posterior to the stomach; largest lymph organ which functions to produce white blood cells, remove abnormal blood cells, and aid in immunity
Adrenal Glands – located superior to each kidney
Right is located just posterior to IVC, medial to the posterior part of the right hepatic lobe – lower and more medial than the left
Left is triangular shaped
Both produce more than 2 dozen hormones including corticosteroids

18. Spleen and Adrenal Glands

19. Kidneys
Bean shaped organs lying obliquely on the posterior abdominal wall on either side of the vertebral column, contains medial hilum where renal arteries and veins enter
Gerota’s (Renal) Fascia – protective layer anchoring the kidneys to the surrounding structures
Renal Cortex – outer third containing the nephrons (functional unit of kidney)
Renal Medulla – consists of renal pyramids which contain the loops of Henle (beginning of collecting system)
Renal Pelvis - kidney has 7-14 minor calyces which merge into 2 – 3 major calyces…they merge together to form renal pelvis
Largest point of collecting system which is continuous with the ureter
Filters blood of impurities and begins transportation out

20. Kidneys
Ureters – muscular tubes transporting urine to the urinary bladder in the pelvis

21. Stomach
Located under left dome of diaphragm and responsible for early digestion
3 Parts
Fundus – superior
Entry is through cardiac orifice
Body – largest
2 curves – Lesser and Greater
Pylorus – empties into duodenum through pyloric sphincter
Rugae – prominent folds when stomach is empty

22. Small Intestine Loops of bowel approx. 6 – 7 meters in length
3 portions
Duodenum – short, begins following pylorus and curves around head of pancreas
Bulb – 1st 2 inches
Jejunum – 2.5 meters long, bulk of digestion occurs here
Ileum – Lower 3/5, longest portion
Ileocecal Valve – termination of small bowel

23. Large Intestine Functions to reabsorb water and excrete feces
1.5 meters in length, “Frames” the small intestine, large diameter and thinner walls
Taenia coli – bands which form the haustra pockets
Parts:
Cecum – at ileocecal valve
Veriform appendix – attached to cecum
Colon:
Ascending – On right
Hepatic flexure
Transverse
Splenic flexure
Descending
Sigmoid
Rectum

24. Abdominal Aorta Located in retroperitoneum
Extension of thoracic aorta through the diaphragm and descends just left of the midline next to vertebrae
At L-4, Bifurcates into the common iliac arteries

25. Abdominal Aorta Branches in order descending…
Inferior Phrenic – Paired
Celiac Trunk – divides into left gastric, common hepatic and splenic arteries
Superior Mesenteric Artery (SMA) – Level L-1 – feeds pancreas and both small and large intestines
Suprarenal
Renal – L-1 / L-2
Gonadal
Inferior Mesenteric Artery (IMA) – Level L-3/4

26. Abdominal Aorta

27. Inferior Vena Cava
Largest vein in the body carrying blood from the lower limbs, pelvis, abdominal viscera and wall
Formed by union of common iliac veins at level of L-5
Passes through posterior surface of the liver and ascends through the diaphragm to the heart
Has tributaries:
Renal Veins – IVC at L-2
Hepatic Veins – IVC at level of diaphragm

28. Visualized Abdominal Muscles
Psoas Muscle – extends along lateral surfaces of the lumbar vertebrae
Rectus abdominus – anterior surface of the abdomen and pelvis
Linea Alba – longitudinal band of fibers found at midline anteriorly
External and Internal Oblique – outer lateral portions of the abdomen until crest

29. Indications for Abdominal Imaging
Metastatic Workup
Abscess
Abdominal Pain
Presenting Right Lower Quadrant Pain – Appendicitis?
Presenting Left Lower Quadrant Pain – Diverticulitis?
Presenting Flank or Lower Back Pain – Renal Colic?
Liver Function and Structure
Pancreatic Pathologies
Hernia – Hiatal means Chest!
Aneurysm of Abdominal Aorta

30. Patient Preparation
If exam is done with I.V. contrast patient must be NPO 4-6 hours
Lab work for I.V. contrast exams
Oral contrast can be given the night before and the morning of the exam, or can be given 2 hours before the exam
Oral contrast can be given at a constant rate of 900ml over a 45 minute period, 200ml is given at the time of the exam to distend the stomach
Air contrast can also be used to give a negative (black) appearance

31. Effusion and infiltration Trauma Pulmonary Parenchymal diseases
Parameters
Single Slice
4 SLICE
16 SLICE
PATIENT
FEET FIRST. SUPINE
SAME
SCANNING AREA
ABOVE LIVER TO SYMPHSIS PUBIS
CONTRAST
100ML AT SECOND DELAY
DETECTOR COLLI NA
4X2.5MM
16X1.5
DFOV
DEPENDS ON PATIENT
SLICE THICKNESS
5 MM
SAME OR SMALLER
ANGLE
NONE
TABLE FEED/ROT
6MM
12.5MM
24MM
PITCH
1 OR 1.5
VARIES
ROT TIME
1 SEC
0.5 SEC
RECON
STANDARD/LIVER IF NO I.V. CONTRAST
WINDOW
450W/30L
Lung nodules
Cancer
Vascular disease
Effusion and infiltration
Trauma
Pulmonary Parenchymal diseases
Hilar Masses

32. Abdomen CT 2 1 3 1 – Liver 2 – Rt. Venticle 3 – Lt. Ventricle 4 – IVC
5 – Azygos Vein
6 - Abdominal Aorta
7 – Rt. Atrium 7 6 4 5

33. Abdomen CT 3 2 1 1 – Rt Hepatic Vein 2 – Middle Hepatic Vein
3 – Left Hepatic Vein
4 - IVC 4

34. Abdomen CT 2 1 1 – Middle Hepatic Vein 2 – Left Hepatic Vein
3 – Stomach
4 – Right Hepatic Vein
5 – Caudate Lobe of Liver 3 6 4 5

35. Abdomen CT 1 – Lt. Portal Vein 2 – Portal Vein 3 – Falciform Ligament
4 – Celiac Artery
5 – IVC
6 – Lt Kidney
7 - Splenic Artery
8 – Spleen
9 – Splenic Flexure
10 – Adrenal Gland
Abdomen CT 3 1 2 4 9 8 7 6 10 5

36. Abdomen CT 3
1 – Rt Adrenal
2 – Pancreas
3 - SMA 2 1

37. Abdomen CT 3 2 1 6 1 - Duodenum 2 – Duodenal Bulb 3 – Pylorus
4 – Left Renal Vein
5 – Pancreas
6 - SMA 5 4

38. Abdomen CT 5 1 2 1 – Transverse Colon 2 – SMA
3 - Small Intestine (Jejunum)
4 – Renal Artery
5 – SMV 3 4

39. Abdomen CT 2 1 1 – Hepatic Flexure (Ascending Colon) 3
2 – Transverse Colon
3 – Descending Colon 3

40. Abdomen CT 3 1 2 4 1 – IVC 2 – Linea Aspera 3 – Rectus Abdominus
4 – Aorta
5 - Psoas 5

41. Phasic Studies of Liver
A three phase CT scan, usually of the liver, requires an injection of contrast medium which helps outline the vessels of your body by giving the x-rays something to be absorbed by besides blood which has a very low absorption rate. The phases are: 1. Scan during injection: Arterial Phase, this will highlight lesions in or around the artery leading into the liver. 2. Scan during injection or shortly after: Portal Venous Phase, this will show lesions in or around the portal vein. 3. Delayed scan after injection: Equilibrium Phase, this will allow the soft tissue to absorb the contrast and may highlight changes in tissue.

42. Parameters Single Slice 4 SLICE 16 SLICE
PATIENT
FEET FIRST. SUPINE
SAME
SCANNING AREA
ABOVE LIVER TO SYMPHSIS PUBIS OR ASIS
CONTRAST
ML @ 2 -4 CC/SEC
PHASE 1 – NON CONTRAST
PHASE 2 – 30 SECONDS
PHASE SECONDS
DETECTOR COLLI NA
4X1MM 4X1.25
16X X1.25
DFOV
DEPENDS ON PATIENT
SLICE THICKNESS
5 MM
1-5 MM
ANGLE
NONE
TABLE FEED/ROT
4MM
VARIES
PITCH
1.5
ROT TIME
1 SEC
0.5 SEC
RECON
STANDARD
WINDOW
450W/30L

43. Phasic Studies of Liver

44. CT Urography
Test of choice for many urologic problems, including urolithiasis, renal masses, urinary tract infection, trauma, and obstructive uropathy.
CT urography provides a detailed anatomic depiction of each of the major portions of the urinary tract--the kidneys, intrarenal collecting systems, ureters, and bladder--and thus allows patients with hematuria to be evaluated comprehensively.

45. CT Urography